They broke ground in Barcelona in 1882.
Upon its completion, La Sagrada Familia was to be a fantastic Catholic basilica, standing 170m high at its peak.
Gaudi, the man who designed La Sagrada's awesome peculiarities, knew he'd probably never see his masterpiece complete.
"My client is not in a hurry," Gaudi is said to have remarked.
With luck and sufficient funding, construction on La Sagrada will finally end in 10-12 years.
I remember - and I'm sure many who have visited Barcelona will relate - being startled by the audacity of Antoni Gaudi's work. Do I like his design? Is it tasteful? Is it pretty? Or is some of it just a bit Dr Seuss?
These are different questions. But I still find beauty in Gaudi's ability to get his ideas from sketches into stone. The gall required to pitch La Sagrada is as impressive as his imagination was rich.
Although there are few certainties in the world of construction, we are assured long before La Sagrada Familia is completed, a version of the Hyperloop will exist.
Elon Musk's large-scale pneumatic tube transport system should have a test track up and going within the next six months. Photos of the prototype have the nerdiest quarters of the internet quivering in anticipation and delight.
Art and science blur, but few people on Earth in 2016 have the Gaudi-esque ability to turn the most audacious ideas into nuts and bolts.
But, just as is the case for most of Elon Musk's design, the Hyperloop shapes up on paper as a genius piece of complicated simplicity: A capsule nestles inside a lengthy tube, where an air vacuum dramatically reduces friction.
Propelled by electricity, the capsule glides through the tube without emissions or a human driver.
Theoretically, the pods will travel at speeds up to 1000km/h, and people and freight could cover enormous distances in crazy-little time.
Helsinki to Stockholm? Under 30 minutes. Sydney to Melbourne? Less than an hour.
The Hyperloop could revolutionise global commerce.
Then again, it might not.
Maybe the whole thing will be a total dud. For all the dreamers and design dorks there are plenty of engineers and critics who think the Hyperloop amounts to little more than an over-egged, over-resourced pipe dream (ba-ba-boom!).
Plenty reckon the whole thing would never have been funded if the design didn't come from Elon Musk.
And on that point, they're right.
If you or I had called a press conference on a Tuesday afternoon and released exactly the same sketches and plans, somehow I doubt we'd have immediately drummed up $100 million in venture capital funding.
Perhaps we could've given the same explanation that Musk did for open-sourcing his design and making it available for anyone to plunder and tinker with - he's too busy running Tesla Motors and working out how to get mankind to Mars - but even then, the Hyperloop needed a hyper-name to get it going.
Elon Musk strikes me as classic, poetic example of a human being who operates at a different level.
He probably can't sit through a movie. He probably can't tie his own laces or make a cup of tea. And honestly, you just know he'd be a nightmare to flat with.
But if history teaches us anything about human genius, it's that genius takes broader nourishment to realise potential.
I'm not Elon Musk. Sorry, but unless you're actually Elon Musk you're probably not Elon Musk, either.
The Hyperloop may crash and burn and never move past the prototype stage. Or then again, it could change the world.
I'm just thankful someone's giving it a crack.
Jack Tame is on NewstalkZB, Saturday, 9am-noon.